BQ500211A Datasheet, PDF (16/27 Pages) Texas Instruments – 5-V, WPC1.1 Compliant Wireless Power Transmitter Manager

bq500211A
SLUSBB1 – DECEMBER 2012
www.ti.com
Current Monitoring Requirements
The bq500211A is WPC1.1 ready. In order to enable the PMOD or FOD features, current monitoring must be
provided in the design.
Current monitoring is optional however, it is used for the foreign metal protection features and over current
protection. The system designer can choose not to include the current monitor and remain WPC1.0 compliant.
Alternately, the additional current monitoring circuitry can be added to the hardware design but not loaded. This
would enable a forward migration path to future WPC1.1 compatibility.
For proper scaling of the current monitor signal, the current sense resistor should be 20 mΩ and the current
shunt amplifier should have a gain of 50, such as the INA199A1. The current sense resistor has a temperature
stability of ±200 PPM. Proper current sensing techniques in the application hardware should also be observed.
Over-Current Protection
The bq500211A has an integrated current protection feature which monitors the input current reported by the
current sense resistor and amplifier. If the input current exceeds a safety threshold, a fault is indicated and power
transfer is halted for one minute.
If this feature is desired, the sense resistor and amplifier are required. If this feature is not desired, the I_SENSE
input pin to the bq500410A (pin 42) should be grounded.
NOTE
Always terminate the I_SENSE pin (pin 42), either with the output of a current monitor
circuit or by connecting to ground.
MSP430G2001 Low Power Supervisor
This is an optional low-power feature. By adding the MSP430G2001, the entire bq500211A is periodically shut
down to conserve power, yet all relevant states are recalled and all running LED status indicators remain on.
MSP430 Low Power Supervisor Details
Since the bq500211A needs an external low-power mode to significantly reduce power consumption, one way of
positively achieving that goal is to remove its supply and completely shut it down. In doing so, however, the
bq500211A goes through a reset and any data in memory would be lost. Important information regarding charge
state, fault condition and operating mode would be cleared. The MSP430G2001 maintains the LED indication
and stores previous charge state during the bq500211A reset period.
The LEDs indicators are now driven by the MSP430G2001, do not exceed the pin output current drive limit.
Using the suggested circuitry, a standby power reduction from 300 mW to less than 90 mW can be expected
making it possible to achieve Energy Star rating.
The user does not need to program the MSP430G2001, an off-the-shelf part and any of the available packages
can be used as long as the connections are correct. The required MSP430G2001 firmware is embedded in the
bq500211A and is boot loaded at first power up, similar to a field update. The MSP430G2001 code cannot be
modified by the user.
NOTE
The user cannot program the MSP430G2001 in this system.
All Unused Pins
All unused pins can be left open unless otherwise indicated. Pins 1, 3, 45 can be tied to GND and flooded with
copper to improve ground shielding. Please refer to the pin definition table for further explanations.
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